In accordance with the prior art, cigarette packaging machines normally comprise a supply unit within which a paper strip unwound from a spool is supplied via a plurality of operating units to a deflection pulley about which the strip is wound and then continues its path above the horizontal bench.
The upper branch of a belt, normally of textile, air-permeable, material and of a closed circuit type, is interposed between the bench and the paper strip.
In the vicinity of this deflection pulley, the strip of paper which is moved along the horizontal bench together with the belt of textile material, receives a continuous carpet of cut tobacco from above.
During its travel along the bench, the paper strip is forced by the belt to fold progressively in a transverse direction so as to form a continuous cylinder full of tobacco, commonly called a continuous cigarette roll, from which the individual cigarettes are obtained by a cutting operation.
When, during the operation of the machine, the paper strip breaks upstream of the deflection pulley, a sensor, normally provided along the path of the strip, automatically shuts down operation of the packaging machine, thus enabling an operator to take the necessary action.
One of the most difficult operations which the operator must carry out to re-activate the packaging machine is to rewind the paper strip about the deflection pulley and to thread it through the very narrow space between the bench and the end of a conveyor for the carpet of tobacco.
An operation of this type, which is difficult to carry out on a machine having a single cigarette roll, becomes almost impossible when it has to be carried out on a machine having a double cigarette roll, or which is able to produce two cigarette rolls simultaneously.
In effect, in this latter case, there are two paper strips which have to be wound around respective coaxial pulleys disposed at the inlet of the bench for the formation of the rolls. As a result of this, one of these pulleys is completely covered by the other and makes access impossible for the operator.
In the U.S. Pat. No. 4,336,813 in the name of the applicants the insertion of the paper strip into the bench for the formation of the roll is automated in an attempt to solve this problem.
In accordance with this patent, cylindrical surface of the deflection pulley placed at the inlet of the bench for the formation of the roll is connected to a suction source.
The operator, therefore, simply has to bring the head of each paper strip into the vicinity of the return pulley, which takes up the strip contacting its outer surface by suction, and, after rotating, feeds the strip to the bench for the formation of the roll.
In an embodiment of the device described in U.S. Pat. No. 4,336,813, the pulley which may be connected to a suction source, forms a return means for the paper strip and also the belt of textile material supporting the paper strip on the bench for the formation of the roll.
It has, however, been found that in these conditions the paper strip does not obey, as a result of its adhesion to the textile material belt in the curved section formed by the deflection pulley, any commands for transverse displacement with which it is supplied by a deflection device controlled by a control device.
In a second embodiment of the device set out in U.S. Pat. No. 4,336,813, the paper strip and the textile material belt are inserted on the roll formation bench by winding about two different return rollers, with the result that the paper strip is superimposed on the belt after the latter has been inserted on the horizontal bench surface.
With respect to the first embodiment, this embodiment has the advantage of a paper strip which is extremely sensitive to transverse displacement commands, but makes it necessary to provide a fixed horizontal bridge, interposed between the two return rollers, which is designed, after each shutdown of operation, to support and guide the head of the paper strip moved by the suction return roller until it is superimposed on the strip of textile material.
The second embodiment has not proved particularly reliable either, since the fixed bridge may cause blocking or folding of the head of the strip as a result of friction with consequent interruptions in its supply.